Field of the Invention
The present invention relates to an amplifier which combines outputs of a plurality of amplifying elements to obtain high output power.
Background Art
Japanese Patent Laid-Open No. H10-327031 discloses a high-output power amplifier including a plurality of amplifying elements. When signals of different phases are supplied to a plurality of amplifying elements, phase differences occur between the signals, and combining efficiency at the time of combining the signals decreases. To avoid this, in the amplifier of Japanese Patent Laid-Open No. H10-327031, a transmission line for sending a signal to an amplifying element through a short wire is lengthened, and a transmission line for sending a signal to an amplifying element through a long wire is shortened.
As described above, it is preferable that signals of the same phase are applied to a plurality of amplifying elements. However, in the case where the lengths of transmission lines are adjusted as in Japanese Patent Laid-Open No. H10-327031, it is not easy to realize high impedance characteristics of wires with transmission lines on a substrate, and a phase difference and an impedance difference cannot be sufficiently reduced. Accordingly, an imbalance occurs in the amplifier of Japanese Patent Laid-Open No. H10-327031. There has been a need for an amplifier which can reduce the imbalance and which is suitable for miniaturization.